Electrical heating element



Jan. 19, 1932.A Q T, JQHNSON 1,842,174

ELECTRI CAL HEATING ELEMENT Filed NOV. 4, 1929 ATTORNEY Patented Jan. 19, 1932 UNITED STATES PATENT OFFICE CLAUDE T. JOHNSON, OF EAST ORANGE, NEW JERSEY, ASSIGNOR TO THOMAS A. EDISON, INCORPORATED, 0F WEST ORANGE, NEW JERSEY, .A CORPORATION OF NEW JERSEY ELECTRICAL HEATING ELEMENT Application led November 4, 1929. Serial No. 404,581.

This inventionrelates to electrical heating elements and particularly to a heating element adapted for use in connection with electrietoasters and the like.

It is an object of this invention to provide a heating element which involves a relatively small number of parts and which may be completely assembled as a mechanical and electrical unit and then mounted with its associated apparatus. f

It is affurther object of this invention to provide a unit which after assembly will have considerable mechanical strength and will maintain its own form with little support from associated elements or casings and which will maintain the desired space relation vwith other apparatus or parts even under the severe conditions of use involving wide temperature variations.

It is a further object of this invention to provide such an arrangement which may be easily and quickly dismounted as a unit from its associated apparatus for inspection, repair or the like and may easily and quickly be replaced therein. n

Still other objects and advantages in my invention will be apparent Jfrom the speciiication.v The features of novelty which I believe to be characteristic of my invention are set vforth with -particularity in the appended claims. My invention itself, however, both as to its vfundamental principles and as to its particular embodiments will best be understood by reference to the specification and accompanying drawings in which- Fig. 1 is a front elevation view of a heating unit according to my invention;

Fig. 2 is a section on lines 2-2 of Fig. 1, and f Fig. 3 is a sectional view showing the unit in position in a casing.

In accordance with my invention I provide an outer frame and an inner frame, the outer frame being designated as 1 and the inner frame as 2. Each of these frames is preferably rectangular and corresponds in general to the shape of the heating elements desired. Both the inner and outer frames are provided with rectangularly disposed portions spaced at intervals around the frame, the

construction being such that as will beseen from Fig. 2, the inner frame may be nested within the outer frame. The angularly disposed portions 3 and l attached to the outer and inner frames respectively provide between them a space within which may be clamped the mica sheets 5, (3, 7 and 8 ou which the electrical heating resistance element 16 is positioned.

In constructing the heating unit the various sheets of insulating material such as mica 5, 6, 7 and 8 are first positioned slightly overlapping and secured in such position by means of eyelets, 17 thus forming a composite sheet of greater dimensions than could be economically provided by means of a single integral sheet. The insulating sheet is provided with holes spared as desired throughout the sheet and the resistance element is wound upon the insulating sheet by threading back and forth through the various holes in the pattern desired.

A fter the resistance wire is mounted upon the insulating sheet the sheet is positioned within the outer frame andthe inner frame is positioned over the sheet and within the outer frame thereby clamping the insulating sheet between the angularly disposed sections 3 and 4. The outer frame 1 is provided with a plurality of ears 9 spaced around the frame, which ears maybe bent inwardly and over the inner frame 2 to secure the said frame in position.

For the purpose of more rigidly maintaining the position and space relation of the insulating elements and its resistance wire, I may provide a plurality of cross braces having angular-ly disposed end portions 11 which lie against the inner frame 2 and which are held in position by means of the ears 9 which are bent over the angularly disposed portions. At one or more intermediate points on the cross braces 1OI may provide studs 12 provided at their extremities with reduced portions 13 which may be passed through holes in the insulating sheets and headed over to maintain the sheet in position.

In order to mount the heating units so constructed in a support or casing there may be provided a dish shaped casing 18. The

assembled units may simply be positioned within the casing 18 as shown in Fig. 3 and riveted in position by means of rivets 19. From this it will be seen that the unit may be easily and quickly constructed and assembled in position with a minimum of labor.

I have shown electrical contacts 14 and 15 mounted in the mica sheets 7 and 6 respectively from which contacts the resistance element 1G is taken. I have also indicated the turns of resistance element 16 as being nonuniformly spaced across the mica sheet, be-

ing spaced closer together at the lower p0rtion of tlie sheets and further apart at thc upper portion thereof for the purpose of providing a more uniform distribution of heat, but itvill be understood the resistance element may be positioned in any particular manner found best suited for the conditions of use.

It Will be noted that the provision of the cross braces 10 permits the anchoring of intermediate portions ofthe mica sheets in position while at the same time the spacing of other portions of the cross braces 10 .from the sheets permits expansion and contraction with minimum danger of buckling the sheets.

If for any reason it is desired to remove one of the heating elements from its casing 18, it is merely necessary to remove the rivets 19 after which the entire heating element may be `taken out as a unit.

While I have shown and described certain preferred embodiments l'in my invention, it will vbe understood that modifications and changes may be made without departing from the spirit and scope of my invention, as will be understood by those skilled in the art and that while I have shown certain preferred constructions I wish it to be understood that the construction shown and described herein is intended as illustrative only and not in limitation Within the scope of the appended claims.

I claim:

1. An electrical heating unit of the resistance type, v'comprising in combination, a 'frame having inner and outer supports'each support having a port-ion lying in the plane of'said unit and another portion angularly disposed thereto, Y an insulating support mounted between said inner and outer supports in the plane of said unit, cross braces secured to said frame and extending across said insulating supp-ort and secured thereto and a resistance clement carried by said insulating support.

2. An electrical heating unit of the resistance type, comprising in combination, a frame having inner and outer support-s, each support being in the form of a strip disposed at an angle to the plane of the unit and having cooperating portions extending therefrom in the plane of said unit, a sheet of insulating material secured inr association with said portions, cross braces secured to said frame and extending across said sheet of insulating material and secured thereto, at an intermediate point, and a resistance element carried by said insulating support.

3. An electrical heating unit of the resistance type, comprising in combination, a frame consisting of inner and outer supports, each support comprising a strip disposed at lan angle to the plane of said unit, said strips comprising cooperating portions extending in the plane ofV said unit, a sheet of insulating material clamped between said portions, cross braces extending over said sheet and secured thereto at an intermediate point and having portions extending along said support, one ofsaid supports having portions adapted to be bent over the other support, and said portions of said cross braces, anda resistance elen'ient disposed on said sheet.v

Il. An electricalv heating'unit of the resistance type, comprising in combination a frame consisting of inner and outer supports, said supports being respectively L shaped in cross section in parts thereof, and comprising cooperating portions normalto-the plane of said unit and portions extending in the plane of said unit, said outer supportcomprising ears extending over saidfinner supportto thereby maintain the position thereof, an insulating support clampedbetween said outer and inner supports, cross braces having portions` clalnpedunder said ears and extending over said insulating support and secured thereto at an intermediate point, and a resistance elementdisposed on said insulating support.

This specification signed this 2nd' day of Nov. 19:29.

e CLAUDE T. JOHNSON.

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